The present invention relates to a device for visually indicating whether a fastener has been properly secured. More particularly, the present invention relates to a device which yields a continuous and permanent visual indicator that a coupling nut of a hydraulic fitting has been torqued to at least a predetermined minimum required tightening value without having to use a torque wrench.
A problem associated with the use of nuts with fasteners and couplings is that of the nut backing out or loosening. The problem has been associated with vibrational, environmental, and other dynamic factors, which cause short-term loss of pre-load and nut back-off.
This problem is particularly apparent in the aircraft industry. In a study conducted by the Society of Automotive Engineers (SAE), 22% of fluid fittings that contained leakage were attributed to loose fittings due to nut back-off.
The prior art includes products which have tried to address the problem. For example, locking washers, spring washers, prevailing torque threads, deformed threads, plastic thread inserts, anaerobic adhesives, double-nutting, and locking pins have been used for fasteners. For fluid fittings and the like, the most common method of preventing nut loosening is by using a xe2x80x9csafety wirexe2x80x9d, in which a length of stainless steel wire is attached to the nut of the fluid coupling via a small hole. The other end of the wire is tied to a nearby component such that the nut rotation in the loosening direction is resisted by the wire.
The safety wire device, however, is costly, since it is extremely labor intensive. A mechanic must take an extra step to insure the nut stays put by affixing the safety wire device to a nearby component after tightening the nut. Thereafter, an additional step must be taken to twist the wire to eliminate the slack. The method is also prone to produce dangerous foreign object damage, since the wires must be trimmedxe2x80x94the excess of which can end up in moving components causing damage. In addition, since the wires must be cut if the particular fitting requires maintenance and/or routine re-tightening, the cutting produces sharp wire ends which may snag other objects or a mechanic""s hands. The wires also may break while being twisted to remove slack.
Attempts have been made to improve on the safety wire method by attempting to secure the nut to the mating half (the male half) of the coupling. One such convention device is a Moeller fitting, which provides torque resistance to the nut by positioning a pattern of torque xe2x80x9cbumpsxe2x80x9d along the male end of the coupling and corresponding recesses positioned along the interior surface of the nut to receive these bumps when mating the male and female halves. This system, however, requires that both the male and female coupling components conform to the Moeller design; i.e., one must replace both the male and female halves in using the Moeller design.
However, industry professionals attribute the loosening of some, if not most, fluid couplings to improper tightening by a mechanic. The theory is that couplings that have failed or are going to fail were never properly secured and torqued to a minimum value in the first place. This may be attributed to an installation or maintenance mechanic simply forgetting to tighten the fitting with a torque wrench. Visually, there is no indication that a nut has been properly tightened to the appropriate torque value.
For now, an inspector must go through and check all fittings with a torque wrench to insure that they are secured at the proper torque value. Accordingly, additional time and labor must be spent to adequately insure that fittings have been correctly tightened.
Accordingly, there exists a need for a way to ensure that a nut of a fluid fitting has been properly tightened to a particular torque value, to avoid the additional time and costs associated with checking these fittings and avoiding system leakage and/or loss of function caused by fittings which have not been fully tightened coming loose.
The present invention presents a new and unique device for providing both visual indication to signify that the nut of a fluid fitting has been properly torqued, and which also provides anti-loosening characteristics to combat loosening of the nut during use.
The present invention yields a continuous and permanent visual indicator for indicating that a coupling nut of a hydraulic fitting has been torqued to at least a predetermined minimum required tightening value, without a mechanic having to use a torque wrench.
It is an object of the present invention to provide a visual torque indication device for a fluid fitting assembly.
It is another object of the present invention to provide resistance to loosening of the nut from the fitting assembly.
It is another object of the present invention to provide a fitting assembly in which the nut resists back-off.
It is another object of the present invention to provide a torque indication device for a fluid fitting assembly which can be retrofitted to existing fittings.
To accomplish the foregoing objects and advantages, one aspect of the current invention provides a fluid coupling capable of indicating proper tightening includes a fitting body having a flared end with a back side. The fitting body also includes an indicator means spaced a predetermined distance away from the back side. A threaded nut is positioned around the fitting body adjacent the flared end and includes a back end and a shoulder portion spaced away a predetermined distance therefrom. The shoulder portion is concentrically aligned with the back side of the flared end. The fluid fitting also includes a belleville(s) washer positioned around the fitting body adjacent the back side of the flared end. Upon threading and torquing of the nut onto the threaded end of a mated fitting, a first side of the belleville washer engages the back side of the flared end and a second side of the belleville washer engages the shoulder portion of the nut resulting in the compression of the belleville washer. When a predetermined amount of torque has been applied to the nut, the indicator means is visible adjacent the back end of the nut.
An additional aspect of the present invention includes, in addition to the features recited above, a sleeve surrounding the fitting body. The sleeve has a first end positioned adjacent the back side of the flared end and a second end spaced apart therefrom. The compression of the belleville washer after a predetermined amount of torque has been applied to the nut results in the second end of the sleeve protruding from the back end of the nut.
These and other aspects and objects, and many of the attendant advantages of this invention will be readily appreciated and understood by reference to the following detailed description when considered in connection with the accompany drawings.